Thermal conduction in clusters of galaxies

We estimate the thermal conductivity of a weakly collisional magnetized plasma with chaotic magnetic field fluctuations. When the fluctuation spectrum extends over two or more decades in wavevector, we find that thermal conduction is very efficient; the conduction coefficient is only a factor of similar to5 below the classical Spitzer estimate. We suggest that conduction could play a significant role in cooling flows in clusters of galaxies.